In the case of machine tools, there are various replaceable devices or tools, respectively, which are connected to the machine tool by way of standardized interfaces. These herein are predominantly tools which are connected to the machine tool spindle or the motor spindle, respectively, by way of a releasable conical connection, and in which so-called collet chucks are opened or closed, respectively, by way of an axial movement such that the axial force that is required for reliably fastening the tool can be transmitted to the tool, or can later be released again, respectively. The so-called collet chuck, or the clamping elements thereof, respectively, by virtue of the axial adjustment thereof push against a detent/ring, or the spindle shaft, respectively, and on account thereof are braced, or form a counter bearing in relation to the clamping force in order for the tool to be braced.
The function of the collet chuck requires the highest possible accuracy, that is to say that the individual clamping segments have to be produced very precisely and optionally also finished. A collet chuck usually has six clamping segments which are disposed radially about the rotation axis.
Clamping systems of this type for machine tools are known, for example from DE 196 36 701 A1 or DE 35 29 181 A1.
In operation it can readily arise by virtue of the “rough” and “dirty” conditions in machine tools that small shavings or abraded particles, respectively, or the like are lodged with the coolant in the clamping system or between individual clamping segments and the shaft, respectively, leading to a positional modification of the respective clamping element. This leads to inaccuracies in terms of the ideal or nominal position, respectively, of the tool and thus to inaccuracies in the machining of the workpiece. However, these inaccuracies of potentially a few micrometers are often no longer tolerable nowadays and lead to scrap and thus to economic damage.
In some cases, malfunctions and/or impediments of the clamping system or of the individual clamping segments, respectively, can also arise during the operation, that is to say during the subtractive machining using the clamped tool, the malfunctions and/or impediments likewise leading to inaccuracies in the machining of the workpiece. However, these inaccuracies are also no longer tolerable nowadays and lead to scrap and thus to economic damage. In the case of a breakage of a clamping segment fragments can even be hurled away, potentially leading to heavy damage to the machine tool and even to a significant risk for people or to personal injury, respectively.
Moreover, a machine tool is already known from DE 196 30 205 A1, wherein the machining accuracy is to be improved by a machine-independent coordinate system. An optical measuring system that is very complex in terms of construction and cost is installed herein on the machining carriage(s), the optical measuring system by means of inter alia a light beam that is directed onto a fixedly installed receiver and of various evaluation components is intended to detect and as far as possible correct errors in terms of direction, dynamic deformations on account of process forces, etc. This complex optical measuring system is moreover suitable only for specific machine tools, in particular, having main and transverse carriages.